As chance would have it Malcolm Turnbull was to have been at a sod turning for a big Toowoomba bypass project on Monday, in Ian Macfarlane’s Groom electorate, together with Deputy Prime Minister and Nationals leader Warren Truss. Now Truss and his new recruit will be a twosome at the event.

Turnbull pulled out of the sod turning, and earlier from a Sunday fundraiser for Macfarlane – which was then cancelled – against the background of some of the most bitter exchanges we’ve heard within the Coalition in many a year.

Tensions are high. It’s not just the fact of Macfarlane jumping ship from the Liberals, or that the row threatens to take political oxygen from Monday’s big innovation statement, Turnbull’s first major policy initiative.

It’s also the startling reality that the deputy prime minister was part of a plot in which information was withheld from the prime minister for a long time. This must put a serious strain on the trust between Turnbull and Truss, to say nothing of the Liberals and Nationals generally. Liberal concerns are all the deeper because Nationals deputy Barnaby Joyce could soon be deputy prime minister, if Truss quits the leadership next year.

Truss was cautious about the defection despite its big reward – making the Nationals entitled to an extra cabinet spot. He was worried how it would affect relations with Turnbull. Joyce was more gung ho. As the days go by, Truss’ fears are being realised.

Queensland Liberal ministers Peter Dutton and George Brandis are fighting a rearguard action, hoping Macfarlane’s move might be thwarted by the executive of the Queensland Liberal National Party. But the Nationals are confident they have covered their bases and the plan will hold.

Dutton told Sky on Sunday:

I don’t think this is a fait accompli. I think the state executive will have something further to say in relation to this.

Dutton insisted “this race is not yet run” and the state executive “needs to consider the whole issue”, including Macfarlane’s preselection. He said:

As I understand it, Mr Macfarlane’s preselection was only ratified a couple of weeks ago but on the basis that he would sit in the Liberal Party party room, so I think the state executive will contemplate whether that issue needs to be revisited and whether or not this outcome that Macfarlane proposes is realised or not. I think there’s a lot of water to go under the bridge.

Brandis – who was never keen on the merger of the Liberal and National party organisations in Queensland – also said the Macfarlane move could not go ahead unless the state executive, due to meet on Monday week, gave its approval.

“I don’t think this should have happened. I think it’s left a very bad taste in people’s mouths,” Brandis said on Network Ten.

He also stressed that Macfarlane had been re-endorsed for Groom “on the explicit understanding that he would sit in the Liberal partyroom”.

While Brandis said no backbencher could “force a cabinet reshuffle on a prime minister by swapping parties in order to game the system” he admitted there was “no doubt” the Nationals were entitled to their share of ministries under the Coalition formula. “That is governed by nothing other than the iron laws of arithmetic”.

In contrast to the two ministers’ version, Queensland Nationals backbencher Matt Canavan said he understood the LNP executive on Thursday had already agreed to the Macfarlane move, subject to it being approved by the Groom divisional council. This approval is expected.

Canavan said he could understand the Liberals were disappointed but he was:

… not going to take lectures from other politicians about ambition and loyalty. Very few people are in a position to be lecturing about that, given the events of the last few years.

Preposterous as it might sound, bolshie National sources were muttering on Sunday that if the Liberals cut up rough, the Nationals might retaliate by laying claim to the Treasury portfolio.

Liberal feeling against Macfarlane has become very personal in some quarters. Cities Minister Jamie Briggs tweeted:

I’m actually quite surprised that people are shocked by Ian Macfarlane’s behaviour, it’s completely in character.

A rumour spread at the weekend that in his meeting with Turnbull on Wednesday, Macfarlane had demanded back his old resources area, now held by Josh Frydenberg. Macfarlane says there was no discussion between Turnbull and him about portfolios.

Turnbull on Sunday refused to be drawn on the row. Asked whether Brandis was right when he said no backbencher could force a reshuffle by swapping parties, he said:

Well, he is the attorney-general. Far be it for me to question the first law officer of the Crown. But, look, I am not going to entertain a discussion of internal party matters.

Suggestions other Liberals could follow Macfarlane have not turned into reality. Queensland Liberal Scott Buchholz, who has been considering whether to jump, has indicated he is staying put.

In another mood dampener for the Liberals, the weekend saw a swing of more than 13% on primary votes against them in North Sydney, the seat previously held by former treasurer Joe Hockey.

As expected, the byelection was won by Liberal Trent Zimmerman; the 13 candidates did not include a Labor contestant.

Liberals say one factor in the big swing was a voter backlash against Hockey, who had become an unpopular figure. He was seen as unsuccessful as treasurer and then forcing people to the polls in the last year of the parliamentary term by bailing out to become ambassador to the US.

With the vote out of the way, Hockey’s diplomatic appointment will now soon be formally announced.